[PATCH 2/2] KVM: selftests: Test guest_memfd binding overlap without GPA overlap

[ZongYao.Chen@linux.alibaba.com]

From: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>

The guest_memfd binding overlap test recreates the deleted slot with GPA
ranges that overlap the still-live slot.  KVM rejects those attempts from
the generic memslot overlap check before reaching kvm_gmem_bind(), so the
test can pass even if guest_memfd binding overlap detection is broken.

Recreate the slot at its original, non-overlapping GPA and use guest_memfd
offsets that overlap the front and back halves of the other slot's binding.
Expand the guest_memfd so the back-half case remains within the file size.

Fixes: 2feabb855df8 ("KVM: selftests: Expand set_memory_region_test to validate guest_memfd()")
Signed-off-by: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>
---
 .../testing/selftests/kvm/set_memory_region_test.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/kvm/set_memory_region_test.c b/tools/testing/selftests/kvm/set_memory_region_test.c
index 9b919a231c93..15607e0bec90 100644
--- a/tools/testing/selftests/kvm/set_memory_region_test.c
+++ b/tools/testing/selftests/kvm/set_memory_region_test.c
@@ -510,7 +510,7 @@ static void test_add_overlapping_private_memory_regions(void)
 
 	vm = vm_create_barebones_type(KVM_X86_SW_PROTECTED_VM);
 
-	memfd = vm_create_guest_memfd(vm, MEM_REGION_SIZE * 4, 0);
+	memfd = vm_create_guest_memfd(vm, MEM_REGION_SIZE * 6, 0);
 
 	vm_set_user_memory_region2(vm, MEM_REGION_SLOT, KVM_MEM_GUEST_MEMFD,
 				   MEM_REGION_GPA, MEM_REGION_SIZE * 2, 0, memfd, 0);
@@ -526,19 +526,19 @@ static void test_add_overlapping_private_memory_regions(void)
 	vm_set_user_memory_region2(vm, MEM_REGION_SLOT, KVM_MEM_GUEST_MEMFD,
 				   MEM_REGION_GPA, 0, NULL, -1, 0);
 
-	/* Overlap the front half of the other slot. */
+	/* Overlap the front half of the other slot's guest_memfd binding. */
 	r = __vm_set_user_memory_region2(vm, MEM_REGION_SLOT, KVM_MEM_GUEST_MEMFD,
-					 MEM_REGION_GPA * 2 - MEM_REGION_SIZE,
+					 MEM_REGION_GPA,
 					 MEM_REGION_SIZE * 2,
-					 0, memfd, 0);
+					 0, memfd, MEM_REGION_SIZE);
 	TEST_ASSERT(r == -1 && errno == EEXIST, "%s",
 		    "Overlapping guest_memfd() bindings should fail with EEXIST");
 
-	/* And now the back half of the other slot. */
+	/* And now the back half of the other slot's guest_memfd binding. */
 	r = __vm_set_user_memory_region2(vm, MEM_REGION_SLOT, KVM_MEM_GUEST_MEMFD,
-					 MEM_REGION_GPA * 2 + MEM_REGION_SIZE,
+					 MEM_REGION_GPA,
 					 MEM_REGION_SIZE * 2,
-					 0, memfd, 0);
+					 0, memfd, MEM_REGION_SIZE * 3);
 	TEST_ASSERT(r == -1 && errno == EEXIST, "%s",
 		    "Overlapping guest_memfd() bindings should fail with EEXIST");
 
-- 
2.47.3